The invention relates to a two-piece rotary cutting die and its associated rules or cutting blades.
More particularly it relates to a means for insuring easy and accurate rule alignment as well as for insuring against rule damage while the die boards are in any storage position on a floor, shelf, die rack or other storage surface.
Steel rule dies are used for shaping and cutting sheet material, usually corrugated board, into preformed blanks from which various types of containers and the like are subsequently formed.
The cutting dies are usually arcuate, the obtainable production rates being higher than with flat cutting dies.
With a rotary cutting die machine, a pair of cylinders are mounted in a supporting frame with a predetermined gap therebetween.
One of the cylinders, usually the upper one, carries a die plate or board, or a pluarlity of die plates or boards, mounting the appropriate cutting rules (and sometimes perforating rules and creasing rules).
The other cylinder normally mounts a yieldable layer of a plastic material which supports the corrugated board as it is fed between the cylinders during their cooperative rotative movements.
Each of the steel rule dies must be fabricated with care and according to a specific particular application.
An arcuate die plate or plural die plates are provided on which is laid out the appropriate shape, or partial shape, of the blank desired, including lines for cuts, perforations and folds, the layout for the die plate being prepared by a special layout machine which compensates for the arcuate shape of the die plate to provide the proper spacings between the cutting or other rules as they will appear on the arcuate configuration of the conventional plate.
Cuts are then made in the die plate along the particular layout lines in the provision of properly located slots for the reception of the cutting, perforating and creasing rules.
These slots will be discontinuous to allow for continuity at the slot ends between adjacent confronting portions or sections of die plates.
The lower arcuate edges of the steel rules seat against the die cylinder so that the upper edges of the steel rules are a given distance upwardly from the cylinder.
The die plate is made with a precise radius of curvature equal to that of the die cylinder on which it is mounted so that a true fit is achieved and the radius of the plate is not changed as it is tightened down on its cylinder.
Countersunk holes are provided in the die plate through which fasteners can be extended to affix the plate to the die cylinder.